Wrinkling and Alligatoring

The film is setting at two different rates through its thickness, and the surface wins.

A coating cures from the outside in wherever the outside is warmer, drier or more exposed. If the top skins over while the material below is still liquid and still moving, that skin is a fixed area of surface sitting on something that is not yet fixed. As the body underneath continues to move, shrink or release solvent, the skin has nowhere to go but into ridges.

Alligatoring is the same mechanism taken further. Instead of buckling into ridges, a harder and more brittle skin over a softer body splits into the crazed pattern that gives it the name.

What matters practically is that this is a defect of the film itself rather than something that landed on it or something missing from it. Nothing contaminated it and nothing was left out.

They are the same window failing at opposite edges, which is worth holding on to because it decides what you did wrong.

A recoat window has two edges. Recoat after it closes and the coat below is fully cured and inert, so the new coat has nothing to bond to and you get intercoat delamination. Recoat before it opens and the coat below has not finished, so it is still moving and still releasing solvent under a fresh layer, and you get this.

Temperature drives both in opposite directions. A hot slab closes the window early, which is how a crew following the sheet recoats too late. A cold slab delays the window opening, which is how the same crew following the same sheet recoats too soon.

So the two defects have the same root cause, the printed figure not matching the slab, and the fix in both cases is to scale the window for the temperature rather than reading it off the page.

Because that is exactly the condition the defect needs, and sunlight supplies it better than anything else on site.

Direct sun heats the surface of a coating far faster than it heats the material underneath or the slab below that. The top skins, the body stays liquid, and the differential is created for you. This is why you so often see a bay that is perfect in the shade and wrinkled in a band that maps to a window or a roller door.

Radiant heaters do the same thing and are worse, because people point them at a floor deliberately to speed a cure. Heating the air is fine. Heating the surface is what causes this.

The practical rule is to keep direct sun and radiant heat off a curing floor entirely. If the space has to be warmed, warm the air and the slab in advance rather than the film after it is down.

Yes, and it is the most common cause after temperature.

Every product has a maximum film build per coat, and it is on the data sheet for this reason rather than as a suggestion. Beyond it the material cannot release what it needs to release before the surface closes over, so the body stays mobile under a set skin.

Thick coats also generate more heat as they cure, because the reaction is exothermic and a deeper pour holds that heat instead of losing it. That accelerates the inside in a way that makes the movement worse rather than better.

The usual reason a coat ends up too thick is trying to bury something in one pass, whether that is a rough substrate, a colour change or a patch repair. Two coats at the rated build will always beat one at double it, and they will cost less to fix.

Only if the material underneath them has fully cured, and often it has not.

Sanding a wrinkled floor while the body is still soft drags rather than cuts. You tear the skin, expose material that is still mobile, and turn a defect with a pattern into a mess without one.

So the first step is to leave it alone until it is genuinely hard all the way through, which can take considerably longer than the data sheet says because the film that trapped the movement also slowed the cure. Test by cutting through a ridge rather than by pressing the surface.

Once it is fully cured you can grind the ridges flat and recoat. On a light wrinkle that is a reasonable repair. On alligatoring, where the skin has split, the honest answer is usually removal, because you are grinding away a cracked layer to reach sound material and there is often not much of it left.

It depends on whether the film ever finished curing, not on how it looks.

A light wrinkle in a film that has since cured fully is a cosmetic problem with a mechanical fix. Grind flat, abrade the whole area, recoat, and the floor performs normally because the material did eventually complete.

A film that never fully cured is a different matter. Material that stayed mobile under a skin may still be soft months later, and no amount of coating over it makes it load-bearing. That one comes off.

Alligatoring sits closer to the second case. A cracked skin means the two layers of one film are behaving as separate things, and the cracks are a path straight down to whatever is underneath. Treat it as removal unless testing shows otherwise.

The test that settles it is the same one that diagnoses it: cut through and see what is under the skin.

Three controls, in the order they matter.

Build to the rated thickness rather than past it. If something needs burying, use another coat rather than a deeper one, and check the film you are actually laying rather than the one you meant to lay.

Keep direct sun and radiant heat off the film while it cures. Warm the space and the slab beforehand if you need to, and screen the windows and doors that let sun onto a bay. Heating the air is fine, heating the surface is the fault.

And scale the recoat window for the slab in front of you. On a cold slab the window opens much later than the sheet says, so waiting for the printed figure is not waiting long enough. Take the slab temperature with an infrared thermometer, work out when the window really opens, and go past it rather than up to it.